Lens module

Abstract

A lens module includes lenses sequentially arranged from an object side toward an image plane sensor and having respective refractive powers. A second lens of the lenses has a convex object-side surface and a convex image-side surface. A first lens and a third lens of the lenses are symmetrical to each other in relation to the second lens.

What is claimed is: 
     
       1. A lens module comprising:
 a first lens having a refractive power; 
 a second lens having a positive refractive power; 
 a third lens having a positive refractive power; 
 a fourth lens having a refractive power; and 
 a fifth lens having a positive refractive power, 
 wherein the first to fifth lenses are sequentially arranged in ascending numerical order from an object side of the lens module toward an image side of the lens module, 
 the refractive power of the first lens is stronger than the refractive power of the fourth lens, and 
 a shape of the fourth lens is symmetrical to a shape of the first lens. 
 
     
     
       2. The lens module of  claim 1 , wherein the first lens has a meniscus shape convex toward the image side of the lens module, and
 the third lens has a meniscus shape convex toward the object side of the lens module. 
 
     
     
       3. The lens module of  claim 1 , wherein an object-side surface of the first lens is convex, and an image-side surface of the fourth lens is convex. 
     
     
       4. The lens module of  claim 1 , wherein an image-side surface of the first lens is concave, and an object-side surface of the fourth lens is concave. 
     
     
       5. The lens module of  claim 1 , wherein the first lens has a convex object-side surface, and the third lens has a convex image-side surface. 
     
     
       6. The lens module of  claim 1 , wherein the lens module satisfies 1.0<|(1/f1+1/f2)/(1/f3+1/f4+1/f5)|<4.0, where f1 is a focal length of the first lens, f2 is a focal length of the second lens, f3 is a focal length of the third lens, f4 is a focal length of the fourth lens, and f5 is a focal length of the fifth lens. 
     
     
       7. The lens module of  claim 1 , wherein the lens module satisfies 1.0<|(r1+r2)/(r5+r6)|<3.0, where r1 is a radius of curvature of an object-side surface of the first lens, r2 is a radius of curvature of an image-side surface of the first lens, r5 is a radius of curvature of an object-side surface of the third lens, and r6 is a radius of curvature of an image-side surface of the third lens. 
     
     
       8. The lens module of  claim 1 , wherein the first lens and the fourth lens have a negative refractive power.